SwiftMQTT

mqttSession = MQTTSession(
	host: "localhost",
	port: 1883,
	clientID: "swift", // must be unique to the client
	cleanSession: true,
	keepAlive: 15,
	useSSL: false
)

mqttSession.connect { error in
    if error == .none {
        print("Connected!")
    } else {
        print(error.description)
    }
}

let topic = "mytopic" 
mqttSession.subscribe(to: topic, delivering: .atLeastOnce) { error in
    if error == .none {
        print("Subscribed to \(topic)!")
    } else {
        print(error.description)
    }
}

let topic = "mytopic"
mqttSession.unSubscribe(from: topic) { error in
    if error == .none {
        print("Unsubscribed from \(topic)!")
    } else {
        print(error.description)
    }
}

let json = ["key" : "value"]
let data = try! JSONSerialization.data(withJSONObject: json, options: .prettyPrinted)
let topic = "mytopic"

mqttSession.publish(data, in: topic, delivering: .atLeastOnce, retain: false) { error in
    if error == .none {
        print("Published data in \(topic)!")
    } else {
        print(error.description)
    }
}

mqttSession.delegate = self

func mqttDidReceive(message: MQTTMessage, from session: MQTTSession) {
    print(message.topic)
    print(message.stringRepresentation)
}

func mqttDidDisconnect(session: MQTTSession, error: MQTTSessionError) {
    if error == .none {
        print("Successfully disconnected from MQTT broker")
    } else {
        print(error.description)
    }
}

dependencies: [
    .package(url: "https://github.com/aciidb0mb3r/SwiftMQTT.git", from: "3.0.0")
]